1. Field of the Invention
This invention generally relates to wire and cable manufacturing machinery and, more specifically, to a concentric strander with take-off sheaves mounted on the strander and a method for assembling same.
2. Description of the Prior Art
Cables made of copper or aluminum conductor strands have been produced on a variety of machines, including rigid stranders, tubular stranders, double twist bunchers and planetary cage stranders. One strander design that has a number of advantages over the aforementioned machines is the concentric strander. Its advantages include high product quality resulting from constant wire pull, high quality wind, elimination of bobbins in favor of permanently installed product packages, high productivity, reliability and cost efficiency.
Bobbins are supported on one proposed concentric strander on the strander shaft or rotor and arranged co-axially with a machine or strander axis so that they can rotate about the axis. An arrangement of flyers or take-off devices are provided for each bobbin (single version) or for each pair of adjacent bobbins (twin version). The wire to be stranded is directed from the bobbins over the flyer and then guided radially inwardly into the rotor and subsequently axially to the closing head. However, the known concentric strander has a disadvantage in that the cage length may need to be increased to accommodate heavier gauge wires. This is because the guide system includes sheaves with diameters that need normally to be increased for heavier gauge wires, thus impacting on the spacing or separation between the axially spaced bobbins to accommodate such guide sheaves.
Another form of a concentric strander has been proposed that is composed of two rotating cylinders or rotors mounted in parallel on a rotatable frame. Each rotor carries a number of spools from which wires are paid out. While one rotor is operating in a production line, the other rotor can be loaded. As soon as the cable going through the active rotor is completed, the frame with both rotors is rotated 180°, thus moving the passive rotor, with the spools loaded to the exact required wire lengths, into the production line. The empty spools in the initially active rotor are moved to the loading position, and can now be re-filled. The objective of this design is to reduce the “down time” and to increase production. In this machine, each rotor includes a plurality of spools arranged sequentially on one shaft. These spools are mounted on the rotor. When positioned in the production line, the spools rotate about the strander shaft and the wires are pulled off through corresponding openings. As indicated, each cylinder includes a plurality of bobbins mounted on the hollow shaft, the rotor itself functioning as a joint flyer on which sheaves are mounted for each of the bobbins. When producing the cable, the hollow shaft and the rotor are driven by a motor, each bobbin providing a wire or strand through individual outlets in the rotor and guided to the stranding head. However, such a machine with the two rotating cylinders or rotors mounted on a rotatable frame has a number of disadvantages, including cost, as it is expensive to produce the rotor with the take-off sheaves. Also, the rewinding of the bobbins is unnecessarily complicated by the need to spin the frame by 180° in order to align the filled bobbins with the machine line while moving the empty bobbins to the re-filing or re-winding station. Furthermore, the core wire needs to be cut to facilitate the process.
The aforementioned machine thus utilizes an outside guide system in the form of a tube to support the first guide pulley. The initially described concentric strander in contrast uses an inside guide system with a spider support for the pulleys.